The present disclosure relates to an optical element laminate, a backlight including the optical element laminate, and a liquid crystal device including the optical element laminate. In particular, it relates to an optical element laminate that improves display characteristics of a liquid crystal display apparatus.
A large number of optical elements have been used in liquid crystal display apparatuses to improve viewing angle, luminance, and other properties. Examples of such optical elements include sheet-like optical elements such as diffuser sheets and prism sheets.
FIG. 1 shows a structure of a liquid crystal display apparatus of related art. As shown in FIG. 1, the liquid crystal display apparatus includes a lighting device 101 configured to emit light, a diffuser plate 102 configured to diffuse light emitted from the lighting device 101, a plurality of optical elements 103 configured to condense or diffuse light diffused with the diffuser plate 102, and a liquid crystal panel 104.
In recent years, as the size of liquid crystal display apparatus increases, the deadweight and size of optical elements are also showing an increasing tendency. The increase in deadweight and size of optical elements causes deformation of optical elements because the stiffness of the optical elements is insufficient. The deformation of the optical elements affects optical directivity to display surfaces and inflicts a serious problem of nonuniform luminance when viewed from an oblique angle.
It has been suggested that the insufficient stiffness of optical elements can be overcome by making the optical element thicker. However, increasing the thickness of the optical elements increases the thickness of liquid crystal display apparatuses, and advantages of thin, light-weight liquid crystal display apparatuses will be lost. A suggestion is then made to resolve insufficient stiffness of sheet- or film-shaped optical elements by bonding the optical elements to one another with a transparent adhesive (e.g., refer to Japanese Unexamined Patent Application Publication No. 2005-301147).
However, according to the technique disclosed in Japanese Unexamined Patent Application Publication No. 2005-301147, the optical elements are bonded to each other with a transparent adhesive. Thus, the thickness of the liquid crystal display apparatus increases, although the increase in thickness is not as significant as that yielded by the improvement technique of increasing the thickness of the optical elements themselves. There is also a risk that the display characteristics of the liquid crystal display may be deteriorated by the transparent adhesive.
Thus, it is desirable to provide an optical element laminate by which the insufficient strength of optical elements can be overcome while suppressing the increase in thickness of liquid crystal display apparatuses and by which deterioration of the display characteristics of liquid crystal display apparatuses can be suppressed. It is also desirable to provide a backlight and a liquid crystal display apparatus each incorporating such an optical element laminate.